Sunday, December 7, 2014

Stripped and Checked New Engine

Back in March this year, I bought a spare engine in the hope of stripping it down over winter and getting it to the point where I could swap it over with the one currently in the car. Once I got it stripped down however, it was obvious it would need a rebore and a set of new pistons which would make the project too expensive for me. As I only paid £50 for the engine though, the purchase wasn't a total loss as I did manage to get an unleaded head and a heap of other spares from the deal. Also as this was my first engine strip, I did gain valuable much needed experience.

Still determined to have a spare engine, I managed to win an auction on eBay and bagged myself a bargain in the shape of a 998cc block with a 40 thou overbore and matching pistons along with a reworked head and a decent gearbox. When I got it home, the first thing I noticed was the crank felt a bit notchy when it was turned, so the first thing was to get it apart and see why...

Looks good, but I'm not so sure!

The block came part assembled with new bearing shells and new pistons, but I have no history of when the work was carried out so I'm not sure how long ago it was done or who did it. One thing that was obvious is that since the re-bore, the engine has never been used, so it's effectively brand new.

So time to find out why the crank is so notchy, as always though before I turn a single nut I photograph everything so I know what it looked like before I started...

Before the crank can come out, the pistons need to be removed. Taking the big end caps off, I was able to examine the bearings in the caps and while most of them were perfect, some were scratched due to small particles of contamination that had somehow managed to find their way in.

Turning the block on its side, I removed the pistons. I started to label them to keep them ordered but later noticed they were already labeled with an etch gun, presumably as part of the previous restoration work. With the pistons out, I was able to have a look at the other side of the big end shells and unfortunately there were more scratches.

The pistons however looked in excellent condition as they're a brand new set of flat top Nüral +.040 pressfits. Looking on the Mini Sport website, they seem to be retailing at the moment for over £300, so already I'm quids in!.

Also the cylinders looked pretty good too with fresh honing marks visible.

With the pistons now out I was expecting the crank to turn pretty freely but it still felt notchy, so removing it was the only option. Once it was out the source of the problem was revealed, yet more bits had got in and scratched the crank bearings and worse still the crank journals. I can only assume that it was assembled in a dirty environment. Shame really as it means I need to buy a new set of bearings before I reassemble it and get the crank repolished.

Aside from the problems with the bits in the bearings, I'm still very pleased with the purchase. The fact it came with a very good unleaded head, a good gearbox and a new set of pistons means this was the kind of bargain I was looking for. Let's hope it gets me back on track.

Next up is to source a new set of bearings and get the crank repolished...